Gmail could charge for account features like Yahoo mail and Fastmail do.

Android could be legitimately open source, like Linux is. Or they could sell carrier specific distributions, which is something carriers are doing themselves right now but badly.

Chrome would need to operate under the aegis of some company, but that needn't be the same company that runs Google search and Google ads. If that were the case, their abusive ad experiences code may actually be good and not merely reflect a desire to destroy ad companies that aren't Google's DoubleClick. Chrome could also then allow browser login integration into other companies. I'd prefer of Chrome integrated with my Apple accounts, not my Google accounts for example.

Ads itself could be split into two companies---Google search ads (which may or may no be owned by Google search), and DoubleClick which was its own company to begin with before Google bought them.

Of course YouTube would need ads. My point was that YouTube doesn't need to be in the same company as search, not that YouTube doesn't need ads. The ad network would likely need to be split into the new companies that are formed so all the parts that need their own ad network could have it.

Chrome likely could not survive on its own unless search paid for it like they do with Firefox. I am not sure all the products/services that Google has and their individual ability to survive without Google. That is something that would need to be determined by the people involved with a breakup.